In The Order of Things (1966) Michel Foucault said he applied an ‘archaeological’ method to analyse the history of thought. His reason to do so was his conviction that ‘systems of thought’ (the subject of his teaching assignment) are governed by certain rules other than those of grammar and logic; rules that are not a part of the consciousness of the individual subject, because they define the system of conceptual possibilities, which determine the boundaries of thought and knowledge deemed possible, or impossible, in a certain period and a particular domain.

Because these rules governing the ‘discursive formations’ at a given time in history cannot be found in the individual’s intellectual products, they have to be excavated, Foucault thought. His ‘archaeology of thought’ tended to disregard, deliberately, the separate human subject as the fountain of historical ideas. It is more fruitful, according to Foucault, to focus on whatever structured the way people in the past were thinking. The task of the historian of ideas, then, would be to unearth these complexes (or fragments) of structuring rules that, together, constituted the mental order (or thinking-mould) of a former age.

Ernst Jünger remarked that archaeology is a science dedicated to pain. What he meant is that, when the archaeologist uncovers in old layers of the earth the remains of former empires and civilisations of which we no longer even know the names, he will realize – painfully – what has been lost, forever. Mourning becomes the site of excavation. (On Pain, 1934).

This has much to do with Foucault’s conviction that, in studying the systems of thought of former centuries, we will hit upon major discontinuities, which to a certain degree – working from present day premises – prevent our understanding this old culture and its products. The implication of the archaeology of knowledge is that one often is confronted with lost civilisations, even when studying periods (like the seventeenth century) we formerly believed to be rather close to our present time.

Eventually Foucault discovered that the archaeological method he applied had a fundamental weakness. It could compare one ‘discursive formation’ to another, bringing out the differences. But it could not show or explain what caused the transition from one system of thought to another. So Foucault decided to add another method: genealogy. In using this concept he was thinking of Nietzsche’s genealogy of morals. What the genealogical analysis adds to the archaeological unearthing of the fundamental structures of a system of thought is: reconstructing how it resulted from unforeseen turns in history. Thus genealogy supplemented the structuralism of archaeology with the contingent course of history. Both methods were intended to contradict the modernist view of continuous trends, inevitably unfolding in history as if it were a rational process. Foucault remained the ‘anti-Hegel’.